The contribution of personality characteristics such as hostility, depression, and anxiety to coronary artery disease now is well established but our understanding of the intervening pathophysiological mechanisms is limited. This application proposes a test of a general hypothesis that the link between these personality characteristics, specifically hostility, and CAD is driven by a hostility-produced increase in the frequency and intensity of interpersonal conflicts throughout activities of daily living and that the impact of this increased frequency and intensity is lower 24-hour levels of autonomic regulation of the heart. The project represents a collaborative effort linking the expertise in ecological momentary assessment of social interactions and daily activity, the work of Dr. Larry Jamner at UC Irvine, and the experience in assessment of autonomic regulation of the cardiovascular system by Dr. Richard Sloan and colleagues at Columbia University. It is based on 3 independent lines of evidence: 1) that hostility is an independent risk factor for heart disease in healthy subjects; 2) that low levels of cardiac autonomic control confer risk of recurrent cardiac events in patients with heart disease and of future cardiac morbidity and mortality subjects healthy at baseline; and 3) that trait hostility influences the behavioral and physiological responses to challenging conditions. By coordinating ecological momentary assessment of mood, behavior, and situational context and 24-hour ECG recordings, we expect to demonstrate that in comparison to subjects low in hostility, those high in hostility will have more frequent and more intense interpersonal conflicts throughout the day; that each of these conflicts will lead to a decrease in autonomic regulation of the heart in proportion to the degree of hostility; and that the accumulated autonomic responses to conflict throughout the day will lead to lower 24-hour levels of cardiac autonomic control in high hostile compared to low hostile subjects. Other analyses will examine the effect of gender differences in the hostility/autonomic regulation linkage as well as explore how differences in mood and social context also may contribute to autonomic dysregulation throughout the activities of daily living. Thus, we expect to demonstrate how personality traits, in combination with social interactions and behavior throughout the day, drive the risk of CHD through an autonomic mechanism.